1. Field of the Invention
This invention relates to axial flow rotary machines and, more specifically, to the reduction of flow path pressure losses in rotary machines.
2. Description of the Prior Art
A rotary machine of the type described above has a working medium flow path extending axially through the machine. The flow path has an inner wall and an outer wall. In the typical prior art constructions, rows of stator vanes extend radially inwardly from the outer wall; rows of rotor blades extend radially outwardly from the inner wall. Each stator vane conventionally has a platform which combines with the adjacent structure to form a portion of the outer flow path wall. Each rotor blade conventionally has a platform which combined with the adjacent structure to form a portion of the inner flow path wall. During operation of the machine, the working medium flows axially between alternate rows of vanes and blades.
Aerodynamically smooth or continuous flow path walls are desired. Stator vane and rotor blade platforms in known prior art constructions join evenly together with the adjacent structure to form the flow path wall. Examples of known constructions are shown in: U.S. Pat. No. 2,663,494 to Keast entitled "Blading For Compressors, Turbines, and The Like"; U.S. Pat. No. 3,902,824 to Sauer entitled "Blade Lock"; and U.S. Pat. No. 3,904,317 to Cardin et al. entitled "Bucket Locking Mechanism". Although the flow path walls of the prior art constructions are shown as smooth continuous surfaces, manufacturing tolerances on platform surfaces and on the surfaces of contiguous components cause discontinuities along the flow path. The flow path discontinuities impose drag pressure losses on the flowing medium and decreased machine efficiency results.
A dramatic increase in the need to produce energy efficient machines has taken place in recent years because of increased fuel costs and limited fuel supplies. As a result, research efforts are being directed toward improving the aerodynamic efficiency of axial flow rotary machines.